William Swain, who had been one of the incorporators of the Magnetic Telegraph Company in 1845, and a purchaser of a large amount of stock the following year in the Philadelphia-to-Baltimore section of the line, was elected president of the Magnetic Telegraph Company on July 9, 1850. He immediately set out to make the company's lines the best they could be and stated, "I am desirous to have the Magnetic Telegraph Company become a model for other telegraph lines to follow in its manner of conducting business, its correct-ness, promptitude and fidelity to the public."
One area in which he felt an improvement was needed was in the style of insulator used on the lines. Taking James Reid into his office one day and showing him a drawing of what became known as the "egg" insulator, Swain exclaimed, "That is the insulator of the future."
Years later, Frank Pope wrote the following article giving an account of the egg:
About the year 1850 or '51 Wm M. Swain, who was then President of the 'Old Magnetic Line' between New York and Washington designed the well known 'egg insulator.' (Figure 9.) Considering the imperfect state of electrical knowledge at that time, there is a wonderful amount of ingenuity and adaptation to circumstances displayed in this design. It not only stamps its author as a man of decided originality but also of sound practical common sense. It is very much to be regretted, on this account, that he did not remain in the telegraph business the rest of his life.
In designing the model of this insulator Mr. Swain succeeded in combining excellent insulating qualities with the highest degree of strength and durability. The general form of the egg or double cone is the strongest that could possibly have been selected. In fact, it has not been an uncommon occurrence for one of these insulators to be dropped from the top of a high pole upon a stone pavement without material injury. Under the ordinary conditions of exposure in the telegraphic service they are very rarely broken.
The egg insulator, upon an iron support, was also quite extensively used from 1851 to 1860 upon many of the telegraph lines in the Eastern and Middle States.
(Figure 9.)
(Figure 10.)
An insulator (Figure 10.) which was taken from an old Fire Alarm wire in Providence, Rhode Island and, as near as can be ascertained, originated in Boston. As will be seen upon inspection, it is an improvement upon Mr. Swain's model in one very important respect, vis., the narrowness and depth of the inner cavity. Its only drawback is an insufficiency of material, and therefore of strength at the top, above the upper end of the support. Like the Swain model it is designed to be fixed upon an iron arm.
After the egg insulators had been in use several years the wires began to work very badly, and show a great deal of escape in wet weather. This was principally caused by the surface of the glass deteriorating from exposure, and becoming coated with dirt and smoke from locomotives and other sources.
The true cause, however, was not at that time understood or even suspected. The managers of telegraph lines jumped to a conclusion, which, as usual, was an erroneous one that the trouble was owing to the egg insulator being too small at the bottom. A certain distinguished advocate of glass insulation remarked:
'When I find that a parasol is a better thing than an umbrella in a big rain, then I shall begin to believe that the egg glass insulates better than the umbrella.' The iron supports also came in for a large share of the general condemnation.
So all the 'egg glasses' and iron arms were thrown away, and a new era of experimenting commenced.
The above is a very informative account of the egg's development. The CD 701, which was the type used on the Magnetic line, is found primarily in dark-colored green glass. The improved style, CD 701.1, referred to above as having originated in Boston, has been found in some colors which are unusual for insulators. It is apparent that the source of them was a glassworks which also made high-quality ware for household use. These insulators have been found in various shades of green and an unusual beige tint. Fragments of them have been located at the site of the Boston & Sandwich Glass Company in Sandwich, Massachusetts. It is reported that a deformed whole unit was located there also. High-quality stemware and other glass wares were produced at the factory.
Other variants of this general style have been found, those being the CD's 701.3, 701.5, 701.6 and 701.8. The CD 701.3, of which only one specimen has been reported, was found in Pennsylvania. The CD 701.5 and CD 701.6 have been located in areas of the southern states where telegraph lines were constructed during the Civil War. Both of these have the same general size and shape, except that the surface of the CD 701.6 is very coarse, and crude in appearance, and also has a long, extended base. It's possible, although not confirmed, that the same mold could have been used to make the CD 701.5 at an earlier date, and the mold later damaged in some way after which time the CD 701.6 units were produced. This is entirely speculation, and the one soft spot in the theory is that both types have been found on the same line, indicating production of each at about the same time.
The CD 701.8, to date only found in shades of aqua, has been located along what was the "National Road" through Pennsylvania, Ohio and Indiana.
Other styles, although quite different from the regular pin type eggs, are the CD 700 and CD 700.1 styles. These have been located primarily in California. While some of these date as early as the 1850's or 1860's, it seems likely some were produced or a least put in service at a much later date. While these have been termed the "Magnetic Egg" by collectors for many years, this is a misnomer, since the CD 701 was the type used by the Magnetic Telegraph Company rather than this through-pinhole type.
A style with several known variants, this is similar enough to the "flat top" eggs to still be considered a part of the egg family, is the CD 718. There are several different mold variants that were produced as early as the 1850's and into at least the middle 1860's. They were a popular item on early Canadian lines, and were produced there in a vivid rainbow of colors ranging from deep cobalt, cornflower blue, amethyst, dark green, amber, and a very wide range of other exotic colors. This one mold variant has as many colorful variations as any other mold type, and a collection of these along would be a very attractive set. One characteristics these have is a slight indentation or groove which encircles the entire insulator on the shoulder just above the top wire ridge. Some of them also have a small extended ring or collar near the base. Several mold variants have been located in different parts of the U.S.
They range in size from some that are very short, to on exceptionally well-made and extremely tall unit used on a line up Mt. Washington in New Hampshire. Some were also made for Tillotson & Co. while Luther Tillotson's supply house was a 16 Broadway in New York. It seem likely that many of the various CD 718's were manufactured in New York State and New England glasshouses.